I connect to pop3 (telnet localhost pop3) and it works fine but when I type the command "telnet localhost 25" i can see something like:
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.

Then the only thing I can do is to close the console. I tried to type ehlo localhost without result and also tried quit, with the same (no) result.

Hey! It's me again. I solved the problem. Well, not exactly... I have to say that I don't know which the problem was, I restarted the howto, recompiled postfix, etc.. and now it works... But I have another problem:

I've tried to send an email between two same-domain users trought telnet and without AUTH LOGIN and it works. Seems to be a problem with sasl authentication. Is there an easy method to disable it and check Squirrelmail, Thunderbird..etc..?

First, make sure you authenticate with full email addresses, not just with the local part (the part in front of @). Also, please make sure that the local part does not exist as a system user in /etc/passwd or in /etc/aliases.

Ok, I authenticate with full email addresses and there's not user1 on /etc/aliases... I've tried with another user and with non-encrypted passwords but still doesn't work. Do I need to configure DNS server or something that is not mentioned in the howto?